I. Field of the Invention
The present invention relates generally to a dental impression tray.
II. Description of Related Art
Dental impression trays, such as the dental impression tray disclosed in my earlier U.S. Pat. No. 4,619,610, are conventionally used to form dental impressions. These previously known dental impression trays typically comprise a pair of spaced sidewalls having a layer of rigid material extending between the sidewalls so that the sidewalls, together with the layer of rigid material, or optionally a gauze layer, netting, plastic or the like, form a channel.
In order to form the impression, the channel of the dental impression tray is filled with an impression material, such as silicon, and the patient occludes against the rigid material. Once the dental impression material has set, the impression tray together with the now set impression material is removed from the patient""s mouth.
These previously known dental impression trays are typically manufactured in either one-half arch or three-quarters arch. For a one-half arch dental impression tray, the dental impression tray is dimensioned so that the tray extends along substantially one-half arch of the patient""s bite. Conversely, a three-quarters quadrant tray is dimensioned so that the tray extends along a three-quarter arch of the patient""s bite.
One disadvantage of these previously known dental impression trays, however, is that different trays were used in dependence upon whether a half arch or three-quarters arch dental impression was required. This necessarily increased the tooling for the dental impression trays and thus the overall cost of the dental impression tray.
A still further disadvantage of these previously known dental impression trays is that, upon occlusion, the rigid sidewalls of the dental impression trays occasionally bent outwardly during patient occlusion. Due to the rigidity of the tray, however, upon removal of the tray with the formed impression, the tray would xe2x80x9cspring backxe2x80x9d to its original shape so that the impression formed in the dental impression material did not precisely conform to the patient""s bite. Consequently, the bridgework typically formed from the dental impression would oftentimes require time-consuming modification by the dentist in order for the bridgework to properly fit in the patient""s mouth. Indeed, in some cases, such modification of the bridgework was not even possible so that it was necessary to take the dental impression and reform the dental bridgework.
The present invention provides a dental impression tray which overcomes all of the above-mentioned disadvantages of the previously known dental impression trays.
In brief, the dental impression tray of the present invention comprises a pair of spaced sidewalls which are dimensioned to extend substantially a one-half arch of a dental occlusion. A layer of material extends perpendicularly between the sidewalls so that the layer together with the sidewalls forms a channel adapted to receive a dental impression material. The layer of material may be either rigid material or a flexible material, such as gauze.
Unlike the previously known dental impression trays, however, the layer of material extends outwardly from one end of the sidewalls such that the shape of the rigid material corresponds to a three-quarters arch of a dental occlusion. Consequently, when only a one-half arch impression of a dental occlusion is required, the outwardly extending portion of the layer material may be simply and readily removed by the dentist prior to taking the impression. Conversely, when a three-quarters arch impression of a dental occlusion is required, the dental impression material is placed not only between the sidewalls but as well as on the outwardly extending portion of the rigid material, gauze, netting, plastic or the like. This outwardly extending portion, furthermore, extends around the front of the patient""s teeth and is easily visible and accessible by the dentist to ensure that a complete impression is made.
Preferably, the material extending between the sidewalls comprises polycaprolactone which becomes pliable above about 140xc2x0 F. The polycaprolactone thus enables a bite trace to be easily formed in the rigid layer by simply heating the tray prior to taking the dental impression.
Alternatively, however, other materials, such as wax or even a flexible gauze, netting, mesh, plastic or the like, may be used.
In the preferred embodiment of the invention, a frame secured to the sidewalls extends around the end of the rigid layer opposite from its outwardly protruding portion. This frame, which preferably is of one-piece construction with the sidewalls, includes at least one reduced cross-sectional area segment intermediate its ends and optionally the frame may be used in lieu of the sidewalls. This reduced cross-sectional area segment minimizes any spring back between the dental impression tray sidewalls that may occur while taking the dental impression.
Additionally, one or more braces are optionally provided between the sidewalls to lock the sidewalls together against outward flexing. Preferably, a handle extends outwardly from one of the sidewalls and the brace is attached to the handle by a frangible link.